Leaders of Iraq’s Sunni Muslim tribes threatened Friday to rebel against the Islamic State, the first indication that a change of government in Baghdad might allow a new prime minister to rally the country’s divided ethnic and religious groups against the Islamist extremists.

But the Sunni offer to battle the militants came with strings _ possible autonomy and the withdrawal of Iraqi military forces from Sunni areas _ that would be difficult for a Shiite-led government to grant, and Shiite politicians in Baghdad showed little enthusiasm. One, Dhiaa al Asadi, a member of Parliament loyal to cleric Moqtada al Sadr, called the Sunni proposal “very exaggerated and unrealistic.”

U.S. officials have predicted since the Islamic State began its sweep through much of central, western and northern Iraq, often with the collaboration of Sunni tribes, that a more conciliatory government in Baghdad, coupled with harsh rule imposed by the Islamists, would move disaffected Sunnis to rebel. That’s one reason the U.S. pushed so hard for Prime Minister Nouri al Maliki to resign in favor of a replacement who would be more disposed to offer concessions to Sunnis and Kurds.

That happened Thursday, with Maliki endorsing a fellow member of the Dawa party, Haider al Abadi, to succeed him.

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Then Friday came the first suggestion that the U.S. theory might prove accurate: an impromptu televised speech by one of the leading Sunni tribal leaders, Ali Hatem, the head of the Dulaim tribe who has sought refuge in Irbil, the capital of Iraq’s autonomous Kurdish zone, from an arrest warrant issued by the Baghdad government charging him with treason.

Hatem, whose Dulaim clan is the largest in Anbar province, said tens of thousands of Sunni tribesmen and other anti-government groups now supporting the Islamic State would change their loyalties if the new government in Baghdad offered something in return. He said that the Islamic State includes thousands of non-Iraqis who could easily be defeated by Iraq’s much larger complex of Sunni tribes.

All the new government of Prime Minister-designate Abadi must do, Hatem said, is end Iraqi army and Shiite militia activities in Sunni areas, limit government and American airstrikes to Islamic State targets only, and hold a referendum that would grant Sunnis autonomy from the Shiite-led government in Baghdad.

“We will fight them once you return our rights and remove the Maliki militias,” Hatem said.

“Do not worry about Daash,” he said, using a derogatory Arabic acronym for the Islamic State. “We are prepared to cooperate and address this issue and you will see the results on the ground. Daash formed because of the sectarian policies of Nouri al Maliki, and it will be no problem for the tribes of Iraq to remove them if we are supported.”

A second offer of rebellion came from Anbar province in Iraq’s west, where 25 major tribes announced to the French Agence France-Presse news service that they would take up arms against the Islamic State after the group “spilled the blood” of tribal members in a series of previously unreported clashes.

“This popular revolution was agreed on with all the tribes that want to fight ISIS, which spilled our blood,” the agency quoted Sheikh Abdel-Jabbar Abu Risha as saying.

The Abu Risha tribe was a key participant in the American-backed Awakening Councils, a successful attempt by the tribes to push their onetime allies in al Qaida in Iraq out of Anbar in 2007. The Islamic State, the successor to al Qaida in Iraq, took control of most of the province in December.

Other media reports said that clashes northwest of the Anbar provincial capital of Ramadi between the Islamic State and the tribes had killed at least 12 militants, according to police officials quoted in the local media.

Significant questions, however, remain about how much actual support Hatem and his tribal colleagues still have over the tribes in places like Anbar, Salahuddin and Nineveh provinces _ Sunni-dominated parts of Iraq where the Islamic State has dominated since June 9, when its forces overwhelmed Mosul, Iraq’s second largest city and the capital of Nineveh.

Many tribesmen have sworn loyalty to the Islamic State, and whether they would really rebel is less clear. The Islamic State has shown itself ready and able to violently suppress dissent among the tribes in other areas of Syria and Iraq that it controls. A recent revolt by a tribe in Deir el Zour province in Syria ended after the Islamic State captured the ringleaders, beheaded some and crucified others, and then posted videos of mass executions on the Internet to make certain the price of rebellion was known.

The Islamic State also is much better armed than the tribes, with vast amounts of heavy weaponry, worth billions, looted from Iraqi and Syrian government stockpiles. A tribal uprising almost certainly would require the direct military support of the Baghdad government or even American ground and air forces, an unlikely prospect.

Hatem also appears to have made a political blunder by adding to his demand a call for Maliki to face criminal charges for his attacks on Sunni population centers. Shiite leaders were openly dismissive.

Asadi, the Shiite member of Parliament, pointed out that Hatem faces treason charges and “is not in good standing with the government.”

“It is better for Mr. Ali Hatem to sit with his tribes and nominate someone to speak for them” in Parliament, Asadi said.

Another Shiite lawmaker, Ali al Fayeh, laughed when a reporter described Hatem’s demands, adding that Hatem should work through Parliament to resolve the dispute.

“He is out of official power. And he’s wanted, so his speech is worthless,” said Fayeh, who is a member of the State of Law coalition, the same as Maliki and Abadi.